Dmitrii A. Rudakov

The mechanism of the noncatalytic bromination of carboranes was studied experimentally and theoretically. We found that the reactions of o- and m-carboranes 1 and 2 with elemental bromine are first order in the substrate but unusually high (approximately fifth) order in bromine. The calculated energy barriers of these reactions decrease sharply as more bromine molecules are added to the quantum-chemical system. A considerable primary deuterium kinetic isotope effect for the bromination of 2 indicates that the rate-limiting stage is B–H bond breakage. According to quantum-chemical reaction path calculations, the bond breakage proceeds after the intrusion of a bromine atom into the B–H σ-bond. The 9-Br and 9-OH substituents in carborane 1 strongly retard the bromination of the corresponding derivatives. The bromination mechanism of 9-OH-1 is complex and includes neutral, deprotonated, and protonated forms of the carborane. The high experimental kinetic reaction order in bromine, together with quantum chemical modeling, points to a specific mechanism of bromination facilitated by anionic bromine clusters which significantly stabilize the transition state.

Deboration of 1-PhCH2-1,2-C2B10H11 by heating in ethanolic potassium hydroxide afforded Me4N+ [7-PhCH2-7,8-C2B9H11]−which was treated with excess halosuccinimide (NCS, NBS) in acetonitrile or with...

A new method for introduction of one and two iodine atoms into the meta-carborane fragments containing carboxy groups at the core carbon atoms C¹/C² was developed. Reaction proceeded in acetic acid at heating in the presence of concentrated nitric and sulfuric acids.

Synthesis procedures for coordination compounds of iron(II) 1,5,6,10-tetra(R)-7,8-dicarba-nido-undecaborates(-1) (carboranes) with tris(pyrazol-1-yl)methane (HC(pz)₃) of the composition [Fe{HC(pz)₃}₂]A₂·nH₂O (A = (7,8-C₂B₉H₁₂)⁻ (I), (1,5,6,10-Br₄-7,8-C₂B₉H₈)⁻ (II), (1,5,6,10-I₄-7,8-C₂B₉H₈)⁻ (III), n = 0–2) are developed. The compounds are studied by static magnetic susceptibility in the temperature range of 160–500 K, electron (diffuse reflectance spectra), IR, and Mössbauer spectroscopy methods. It is shown that the complexes have high-temperature spin-crossover ¹ A ₁ ⇔ ⁵ T ₂. Transition temperatures (T _c) for I–III are 370 K, 380 K, and 400 K respectively. Spin-crossover is accompanied by thermochromism (color change: pink ⇔ white).

Oximes of β-isatin, isoxazole- and ferrocene-containing ketones, o- and m-carborane alcohols react with isoxazol- and isothiazolecarboxylic acid chlorides in the presence of triethylamine to afford the corresponding esters.

A technique is proposed for directed synthesis of 6,11-dichloro-9-dimethylthio-7,8-dicarba-nido-undecaborane [6,11-Cl₂-9-SMe₂-7,8-C₂B₉H₉]. Single-crystal X-ray diffraction is used to identify the molecular and crystal structure of the compound.

A preparative method for the synthesis of m-carborane azo methines via the condensation of mcarborane- C-4-for mylphenyl methanoate with aliphatic, cycloaliphatic, and aro matic a mines was developed.

A method of preparative synthesis of o(m)-carborane-containing azomethines via the condensation of o(m)-carboranyl-C-methylene-4-formylbenzoates with aliphatic, cycloaliphatic, and aromatic amines was developed.

A air and moisture stable square-planar trans-dichloropalladium(II) complex containing two 5-(p-tolyl)isoxazol-3-amine ligands was synthesized and structurally characterized by single-crystal X-ray diffraction. The isoxazol-3-amine ligand was prepared from 5-(p-tolyl)isoxazole-3-carbaldehyde oxime by successive transformations. The new complex is a high-turnover-number catalyst for the Suzuki-Miyaura reaction with low palladium loading (0.0001-0.1%) in neat water under an air atmosphere.